Maternal serum alpha-fetoprotein (MSAFP) test. For the MSAFP test, a sample of the mother's blood is drawn and tested for alpha-fetoprotein (AFP) — a protein produced by the baby. It's normal for a small amount of AFP to cross the placenta and enter the mother's bloodstream. But abnormally high levels of AFP suggest that the baby has a neural tube defect, such as spina bifida, though some spina bifida cases don't produce high levels of AFP.

Many obstetricians rely on ultrasonography to screen for spina bifida. If blood tests indicate high AFP levels, your doctor will suggest an ultrasound exam to help determine why. 

Amniocentesis- your doctor uses a needle to remove a sample of fluid from the amniotic sac that surrounds the baby.  

Other blood tests. Your doctor may perform the MSAFP test with two or three other blood tests. These tests are commonly done with the MSAFP test, but their objective is to screen for other abnormalities, such as trisomy 21 (Down syndrome), not neural tube defects.